Because of the problems of environmental pollution, there has been increased interest in the separation of oil from bodies of water. Oil slicks on oceans and lakes caused by leakage from tankers, drilling rigs, and storage tanks, has caused serious pollution of beaches and injury to wildlife. Similarly, oil-water mixtures resulting from industrial activities has produced serious pollution problems when discharged into rivers, streams and other bodies of water.
As an example, many machine parts or heat treated parts are washed in wash tanks, and the wash water is contaminated with machine oil and heat treating oil. In the past the contaminated wash water has been discharged into the sewage system, but because of the pollution problem this practice has been discontinued with the result that it is frequently necessary to haul the oil-contaminated wash water away to disposal sites or for further separation treatment.
In an attempt to separate oil from wash water, or other bodies of water, partially submerged float tubes, belts and discs have been utilized which rotate or travel in the wash water and pick up a film of water-oil mixture and the film is subsequently removed from the moving element. Devices of this type have a low efficiency of separation, meaning that it is not possible to remove all of the oil from the body of water, and the removed oil contains a substantial proportion of water. In addition, separating devices, as used in the past, have generally had a low capacity resulting in the removal of only small amounts of oil in a given period of time.
The patent to Maksim U.S. Pat. No. 3,702,297, discloses an oil skimming device in which a drum is partially submerged in the body of water and, on rotation, serves to pick up a film of oil and water which is removed from the surface of the drum by a doctor blade. With the device as shown in the Maksim patent, the oil-water mixture is delivered to a receptacle and the oil separates from the water so that an increasingly deeper layer of oil accumulates in the receptacle and the water is displaced from the bottom of the receptacle. When the oil-water interface descends to a set level, a pump is operated to withdraw the oil from the container and water flows back into the receptacle to replace the oil.